Dielectronic recombination of W20 + (4d104f8): Addressing the half-open f shell

Abstract

A recent measurement of the dielectronic recombination (DR) of W20 + found an exceptionally large contribution from near-threshold resonances (∼1 eV). This still affected the Maxwellian rate coefficient at much higher temperatures. The experimental result was found to be higher by a factor of 4 or more than that currently in use in the 100- to 300-eV range, which is of relevance for modeling magnetic fusion plasmas. We have carried out DR calculations with autostructure which include all significant single-electron promotions. Our intermediate-coupling (IC) results are more than a factor of 4 larger than our LS-coupling ones at 1 eV but still lie a factor of 3 below experiment here. If we assume complete (chaotic) mixing of near-threshold autoionizing states, then our results come into agreement (to within 20%) with experiment below ∼2 eV. Our total IC Maxwellian rate coefficients are 50%-30% smaller than those based on experiment over 100-300 eV. © 2012 American Physical Society.